I've recently been restoring an H8/H17 system. Almost all of
the problems involved capacitors, including a bad electrolytic
in the H17 (diskette unit) power supply. I repaired the H17
supply using a dummy load but apparently the H17 was run with
the bad supply before I got it. I say this because some of the
tantalum caps on the logic boards of the Wangco model 82 diskette
drives popped and/or burned when correct power was supplied to
them. I've seen plenty of the "teardrop" tantalums pop, but I've
never seen one of the "black suppository" types (used on these
drives) go. I believe this was the result of bad ripple in the
supply.
Anyway, one of the Wangcos now runs perfectly and the other runs
fine for a while but fails after about an hour of applied power.
The difference between the two is that, on the flaky drive, a cap
in series with an inductor did a slow burn, resulting in the
inductor having a "nice brown toasty" appearance and a small split
in one side that some red resin leaked from. By the way, the only
way I know this is an inductor is that it is labeled "L5". It
looks like a large beige resistor with too many color stripes on it.
Inductors are a weak area in my electronics knowledge. How would
you know for sure that one has failed? Does it fail open?
Other info: When the drive fails, it can not read any data and,
when seeks are attempted on it, it sounds "funny", not the nice
sharp click it makes when operating correctly. The inductor does
not feel hot to the touch when the drive has failed. I'm out of
cool spray. Tonight I will try to apply an ice cube in a plastic
bag to it to see if that gets it out of failure mode.
Finally, assuming it is the problem, what do I need to replace it?
The stripes on it are:
Wide silver (covering one end)
Red
Yellow
Brown
Gold
Thanks,
Bill